Green synthesis of iron oxide nanoparticles from extracts of <i>Daucus carota subsp. sativus</i> whole vegetable, peel, pomace, and juice and their application as antibacterial agents and Fenton-like catalysts

Abstract The green synthesis of iron oxide nanoparticles (Fe-NPs) with catalytic and antimicrobial activities from the extracts of different parts of Daucus carota subsp. sativus var. atrorubens Alef. was demonstrated in this study. The extracts of whole vegetable, peel, pomace, and juice acted as a reducing agent for the bio-reduction of Fe3+ into Fe-NPs. The synthesis of Fe-NPs was indicated by surface plasmon peaks within the range of 200–300 nm, as well as characteristic iron oxide bond formation in the region of 400–850 cm−1 using an ultraviolet-visible spectrophotometer and FT-IR spectrophotometer, respectively. The green synthesised Fe-NPs from the whole vegetable and its byproduct extracts had uniform quasi-spherical structures, with average particle sizes of 87.13, 80.95, 103.14, and 86.26 nm from whole vegetable extract, peel extract, pomace extract, and juice, respectively. All synthesised particles exhibited excellent Fenton-like catalytic activities on the discoloration of methylene blue best fitting the pseudo-first order kinetic model for Fe-NPs from whole vegetable extract, pomace extract, and juice and the pseudo-second order kinetic model for Fe-NPs from peel extract. In addition to catalytic activity, Fe-NPs showed antibacterial activity against Escherichia coli, Staphylococcus aureus, and Bacillus subtilis. The antibacterial effects of Fe-NPs alone and their synergistic effects with antibiotics have been observed in both Gram-positive and Gram-negative bacteria.